A double pressure cylinder arrangement of the kind referred to is preferably used in the textile machine industry. In a drafting arrangement for fiber material, the double pressure cylinder arrangement is used in a loading device. A drafting arrangement essentially includes a series-connected arrangement of a plurality of top and bottom roller pairs, wherein each top roller may have a force applied to it by means of the double pressure cylinder arrangement in order to press it against the bottom roller. Accordingly, the support of the top roller is usually of the floating type. Fiber material is continuously passed between each top and bottom roller pair and generally drafted by a series connection of a plurality of such drafting arrangements so that the fiber material is subjected to a lasting extension. For this purpose, the individual drafting arrangements have different speeds.
In EP 0 939 151 A2 a drafting arrangement of the above kind is disclosed having a loading device equipped with corresponding double pressure cylinder arrangements. The loading device essentially includes a loading arm for supporting the top rollers of the drafting arrangement. The three top rollers are adjacent to associated bottom rollers. The top rollers are rotatably supported at both ends in corresponding bearings and are pressed against the bottom roller by the loading device in order to create a permanent frictional engagement with the passing fiber material, so the latter can be extended when it passes through the drafting arrangement. The spaces between the top rollers are made to be adjustable because different spaces are required depending on the fiber material to be stretched. The pressure force on the top rollers generated by the loading device is controlled by a pressure of pressurized air applied to the loading device via suitable pressure lines. The loading arm is also pivotable about a pivot point, so that the loading arm may be opened to make the drafting arrangement accessible in the area between the top and bottom rollers when new fiber material is inserted or malfunctions are removed.
Pressurized air may be applied to the double pressure cylinder arrangement of the loading device at the side facing away from the piston so that the pressure force generated in this way is transferred to the two end areas of each top roller via the two piston rods having parallel axes. Each top roller has a separate double pressure cylinder arrangement associated with it.
The prior art double pressure cylinder arrangement is made of two identical standard cylinders attached to a carrier strut at their cylinder bottoms by means of bolts in order to generate the desired parallel, spaced pressure force for the associated top roller. The carrier strut is a bent sheet metal part which is very costly to manufacture. Moreover, the standard cylinders available for the usage referred to have a long structural length, so that the entire double pressure cylinder arrangement extends from the drafting arrangement in an interfering manner. Due to this bulky structure, the pivotable loading arm is also difficult to handle. Additionally, because of the exposed electrical and pneumatic connection lines at the standard cylinders, there is a risk of the lines getting ripped off. The individual parts of the prior art double pressure cylinder arrangements are also difficult to assemble.